A Gram-negative, motile, rod-shaped bacterial strain, designated Ad2(T), was isolated from a marine sponge, Axinella dissimilis, which was collected from a semi-enclosed marine lake in Ireland. Strain Ad2(T) grew optimally at 24 °C, at pH 7.0 and in the presence of 3 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Ad2(T) clustered with members of the genus Pseudovibrio, and showed 97.3-98.2 % sequence similarity to the type strains of recognized Pseudovibrio species. DNA-DNA relatedness values between strain Ad2(T) and the type strains of other Pseudovibrio species were <27 %. The DNA G+C content of strain Ad2(T) was 50.5 mol%. The major fatty acid was 18 : 1ω7c. Differences in phenotypic properties, together with phylogenetic and DNA-DNA hybridization analyses, indicated that strain Ad2(T) represented a novel species of the genus Pseudovibrio. The name Pseudovibrio axinellae sp. nov. is proposed, with Ad2(T) (= DSM 24994(T) = NCIMB 14761(T)) as the type strain.